Method and apparatus for manufacturing internally coated glass tubes

Abstract

The invention relates to a method for manufacturing a glass tube with a coated inner surface by drawing a glass melt (5) to a bag (8) of softened glass and hot forming to a glass tube (9). During the process a substance is introduced into the bag (8) of softened glass. According to the invention the substance is introduced as an aerosol and the inner surface is coated by means of the substance during the hot forming. The method permits economical internal coating with a continuous glass drawing method. The use of aggressive chemical substances for internal coating can be dispensed with according to the invention. As a result, for example, internally coated glass tubes with improved hydrolytic resistance can be manufactured. The invention also relates to a suitable apparatus for manufacturing internally coated glass tubes and the use of glass tubes manufactured by this means for further processing to a hollow, internally coated formed glass body, for example, as primary packaging in the pharmaceuticals field.

Description

FIELD OF THE INVENTION [0001] The present invention relates in general to the manufacturing of glass tubes having an internally coated inner surface, particularly a chemically or physically modified inner surface, by means of a continuous or semi-continuous glass drawing method. The present invention also relates to the use of such glass tubes as semi-finished products for manufacturing hollow formed glass bodies by further forming the semi-finished product into hollow formed glass bodies. BACKGROUND OF THE INVENTION [0002] Technical applications for glass, for example as a starting material for primary packaging materials in the pharmaceuticals industry, increasingly demand hollow formed glass bodies whose inner surface is as chemically inert as possible in that, for example, it releases as few ions as possible into a substance stored within it or reacts as little as possible with a substance stored in the formed glass body. Glasses with inert surfaces can be prepared by suitable c...

AI Technical Summary

Benefits of technology

[0023] According to a further embodiment, an aerosol is formed in a process gas which is blown into the bag of softened glass. This process gas may be, in particular, CO2, noble gases or mixtures thereof, to which oxygen can also be added in a suitable concentration. However, the process gas can in principle also have a larger oxygen content compared to the atmosphere, even to the extent of being pure oxygen, which can be advantageous for the further reaction of the aerosol particles in the hot forming process.

[0024] According to a further embodiment, an aerosol is introduced through an outlet opening at the front end of a forming body, over which the glass melt is drawn. For this purpose, the forming body suitably has an axial inner bore so that the aforementioned outlet ope...

Problems solved by technology

However, the manufacturing of such glasses is frequently relatively expensive.

Furthermore, such glass types are often not able to comply with the required specifications, particularly with regard to their formability into hollow bodies at the lowest possible temperatures.

Methods of this type, however, are subject to numerous limitations.

The cost for suitable modification of the inner surface is therefore shifted onto the manufacturer of the hollow formed glass body, which is frequently undesirable for reasons of cost and suitability.

Due to the usually fundamentally different manufacturing parameters, the principles applied to discontinuous manufacturing methods cannot be transferred to continuous manufacturing methods, or cannot be transferred without further effort, so that they do not offer any inspiration to persons skilled in the art for improving continuous or semi-continuous ...

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